Exam 2: Cranial Nerves

Question 1

Function of the cranial nerves

Answer 1

A. The cranial nerves function to bring in sensory information from facial/neck regions and send out motor commands

1. Dorsal for sensory nuclei and ventral for motor nuclei in both the spinal cord and brainstem cranial nerves
2. THE INNERvation is bilateral

Question 2

WHich nerves have cell bodies in the forebrain?

Answer 2

olfactory and optic

I, II

Question 3

Which nerve has cell bodies in the cervical spinal cord?

Answer 3

spinal accessory (XI)

Question 4

WHICH nerves have cell bodies in the midbrain?

Answer 4

ocular motor and trochlear

III, IV

Question 5

Which nerves have cell bodies in the pons?

Answer 5

trigeminal, abducens, facial, vestibulocochlear (V, VI, VII, VIII)
trigeminal and vestibulocochlear have medulla components

Question 6

WHich nerves have cell bodies in the medulla?

Answer 6

glossopharyngeal, vagus, hypoglossal (IX, X, XII)

Question 7

WHIch nerves are purely sensory in function

Answer 7

CN I, II, VIII

olfactory, optic, vestibulocochlear

Question 8

Which nerves are purely motor in function?

Answer 8

CN III, IV, VI, XI, XII

ocular motor, trochlear, abducens, spinal accessary, hypoglossal

Question 9

WHich nerves are mixed sensory and motor?

Answer 9

CN V, VII, IX, X

trigeminal, facial, glossopharyngeal, vagus

Question 10

CN I - the olfactory nerve

Answer 10

function: smell, somatic sensory
cell bodies: CNS, Primary sensory neurons detects olfactory information in the neuroepithelium in the upper nasal cavities and synapse onto neurons in the olfactory bulb. These neurons make up the olfactory nerve
- After forming olfactory tracts (aka nerves) in the olfactory bulb, the axons synapse onto neurons in the piriform cortex adjacent to the temporal lobe

Question 11

CN II - the optic nerve

Answer 11

function: vision, purely sensory
cell bodies: Retinal ganglion cells in the retina of the eye send their axons, as part of the optic nerve, into the lateral genicukate nucleus of the thalamus
- After synapsing onto neurons in the thalamus, the thalamic neurons then go to the primary visual cortex in the occipital lobe

Question 12

CN III - the oculomotor nerve

Answer 12

function: eye movement, motor only, autonomic and somatic
cell bodies: nuclei for nerve in midbrain
- Contain somatic motor axons (voluntary control, aka lower motor neuron) and parasympathetic axons for pupillary constriction reflexes and ciliary muscles for near vision

Question 13

CN IV - the trochlear nerve

Answer 13

• function: eye movement downwards
• nuclei for the nerve in midbrain
• This nerve is purely somatic motor (voluntary control, aka lower motor neuron)

Question 14

CN VI - the abducens

Answer 14

• function: lateral movement of the eyes
• nuclei for the nerve in the pons
• purely somatic motor

Question 15

CN V - the trigeminal nerve sensory

Answer 15

• function: sensory innervation (touch, pain) of the face (and dura) and motor control of muscles for mastication, which is called the branchial motor root/ touch and pain for face)
• Nuclei for the nerve: in ventrolateral pons. CN V primary sensory neurons synapse onto these nuclei
• 1st neuron: primary sensory neuron
  2nd neuron:
• Chief trigeminal nucleus in pons – for crude touch (medial lemniscus)
• Spinal trigeminal nucleus in pons/medulla-for pain (trigeminothalamic)
• Both sends axons to ventral posterior medial nucleus (VPM) in thalamus
• From the VPM thalamus for both tracts, the thalamic neuron then sends its axons to the primary somatosensory cortex

Question 16

CN V - the trigeminal nerve motor

Answer 16

• The trigeminal motor nuclei contains the lower motor neuron (or second neuron) that will innervate the mastication muscles—in the pons
• An upper motor neuron from the primary motor cortex (primarily) sends its axons down bilaterally to the trigeminal motor nuclei

Question 17

CN VII - the facial nerve

Answer 17

• Function: the main function is to control muscles of facial expression, other functions include tears and salivation and taste (autonomic and somatic)
• Nuclei: facial nerve nucleus in the pons
• Components: visceral motor (branchial), parasympathetic motor and sensory and visceral and somatic sensory
• There is ipsilateral and contralateral control

Question 18

CN VIII – the vestibulocochlear nerve

Answer 18

• Function: hearing and vestibular sensation
• Nuclei: cochlear nucleus in the pons/medulla junction for hearing and the vestibular nuclei in the pons/medulla
• Components: somatic sensory only
  a. A primary sensory neuron that innervates the cochlea sends its axons to the cochlear nucleus
  b. The cell bodies of these sensory neurons ( for hearing) are the spiral ganglia
• 1st neuron=primary sensory neuron in its own ganglia
• 2nd neuron=cochlear or vestibular nuclei (pons/medulla)
• 3rd neuron = thalamus
  medial geniculate for hearing
  Ventral posterior for vestibular

Question 19

CN IX – the glossopharyngeal nerve

Answer 19

• autonomic and
• Function: main function is sensation in the posterior tongue and pharynx (touch, pain and temperature)
• Nuclei: each component will have its own nuclei in the brainstem-most nuclei are within the medulla
• Components: parasympathetic, somatic sensory and visceral motor, visceral sensory

Question 20

CN X – the vagus nerve

Answer 20

• Function: swallowing, voice box, taste in specific regions, heart/lungs/GI tract autonomic innervation
• Nuclei: each component will have its own nuclei in the brainstem-most nuclei are within the medulla
• Components: parasympathetic, somatic and visceral sensory and visceral motor (branchial)

Question 21

CN XI - the spinal accessory nerve

Answer 21

CN XI is purely visceral motor and helps head move. Motor axons travel with CN X vagus so CN XI is considered functionally a part of the vagus. Nuclei are within cervical spinal cord, however

Question 22

CN XII - the hypoglossal nerve

Answer 22

• Function: intrinsic movement of the tongue
• Nuclei: the hypoglossal nucleus in the medulla
• Components: somatic motor